1. Field of the Disclosure
The present disclosure relates generally to apparatus and methods for estimating characteristics or properties of sensors that include an interferometer, calibrating such sensors utilizing the estimated characteristics and such calibrated sensors wellbores for production of hydrocarbons.
2. Description of the Related Art
During both drilling of a wellbore and after drilling a wellbore, a variety of sensors are utilized for determining downhole parameters, including, but not limited to, gravity and acceleration. Gravimeters and accelerometers are often used to make such measurements. Some gravimeters and accelerometers utilize an interferometer that includes a proof mass and parallel partially reflective glass plates. Employing high precision gravimeters and accelerometers in in downhole applications improves accuracy of measurements. Some such sensors utilize interferometers that include a pair of parallel spaced apart partially reflective glass plates to generate optical interference. One way to increase the accuracy of such sensors is to accurately determine the distance between these partially reflective glass plates in wavelengths of light for precision calibration of such sensors. Mechanical measurements are generally are not accurate for precision calibration of such sensors. In some downhole application, it is desirable to have gravimeters that can provide highly accurate measurements over a wide range compared to traditional gravimeters, such as a gravity range between 1 g and 0.96 g. Other useful characteristics of interferometer-based sensors for use in making accurate interferometer-based sensors may include estimation of fringes of the interferometer at various angles of an incident light and the distances between peaks of such fringes.
The disclosure herein provides apparatus and methods for estimating certain characteristics of sensors that utilize optical interferometers, calibrating such sensors and utilizing such calibrated sensors in downhole applications.